EarthBound Beginnings/Battle Engine

Fight

Hit/miss Calculation

The defender dodges if:

(256 + AttackerFight - DefenderFight) / 2 < (RANDOM 0-255) + 102

Otherwise "[NAME] dodged swiftly." If the attacker and defender have equal Fight, the chance of hitting is approximately 90%.

If the attacker is blinded there is an additional 50% chance to miss the attack.

Damage Calculation

The following method is used to determine attack damage:

1. Calculate base damage (round BaseDamage down):

BaseDamage (normal) = [(AttackerOffense * 3) - DefenderDefense] / 4

BaseDamage (SMAAASH!!) = AttackerOffense

2. Get random multiplier from this table. There is a 50% chance of RandMult being negative.

Odds	7.8%	7.8%	7.8%	7.8%	7.8%	7.0%	7.0%	6.3%	6.3%	5.5%	4.7%	4.7%	3.9%	3.1%	3.1%	2.3%	2.3%	1.6%	1.6%	1.6%	0.8%	0.8%	0.8%	0.8%
RandMult	0	±1	±2	±3	±4	±5	±6	±7	±8	±9	±10	±11	±13	±14	±15	±16	±17	±18	±19	±20	±21	±22	±23	±24

3. Calculate final damage (round FinalDamage down):

FinalDamage = BaseDamage * (1 ± 0.1 * RandMult)

This means that any attack can hit for 76% to 124% of its base damage.

Odds of getting a SMAAAASH!!

The chance of a SMAAAASH!! is exactly the same as the chance of missing an attack: The attacker gets a SMAAAASH!! if:

(256 + AttackerFight - DefenderFight) / 2 > (RANDOM 0-255) + 102

If the attacker and defender have equal Fight, the chance of both hitting and getting a SMAAAASH!! is approximately 9%.

PSI

PSI attacks will always hit if the defender is not PSI-protected.

Damage

PSI damage calculation is done in exactly the same way as the Fight damage calculation, but uses base damage given by PSI properties.

Healing

Healing PSI moves heal for the same amount of damage they would do as calculated by the Fight damage calculation, using base damage/healing given by PSI properties.

Turn order

Every turn, everyone in combat is assigned a "final speed" value, calculated as follows. The same RandMult table from the Fight section is used.

FinalSpeed = BaseSpeed * (1 ± 0.1 * RandMult)

Everyone in combat then acts in order of their calculated FinalSpeed, highest to lowest.

Run away

Every non-fainted ally has a 50% chance of successfully running away, and if any one ally escapes the entire party will escape. So, the chance of successfully running away is:

1 - 0.5^{Number of non-fainted allies}

Combat data

Allies

Stored at RAM 0x0600-0x067F

• 00: Ally in party, FF if ally is in party
• 01: Status condition
  • Bit 0: Cold
  • Bit 1: Poisoned
  • Bit 2: Puzzled
  • Bit 3: Confused
  • Bit 4: Sleeping
  • Bit 5: Paralyzed
  • Bit 6: Stone
  • Bit 7: Unconscious (can be applied even when HP isn't at 0)
• 02: Unknown
• 03-04: HP
• 05-06: PP
• 07-08: Offense
• 09-0A: Defense
• 0B: Fight
• 0C: Speed
• 0D: Wisdom
• 0E: Strength
• 0F: Force
• 10-17: Unknown
• 18-19: Pointer to name
• 1A-1F: Mostly unknown
• 1E:
  • Bit 1: Having asthma attack
  • Bit 5: Roped
  • Bit 7: Blinded

Enemies

Stored at RAM 0x0680-0x06FF

• 00: Unknown
• 01: Status condition
  • Bit 0: Cold
  • Bit 1: Poisoned
  • Bit 2: Puzzled
  • Bit 3: Confused
  • Bit 4: Sleeping
  • Bit 5: Paralyzed
  • Bit 6: Stone
  • Bit 7: Unconscious (can be applied even when HP isn't at 0)
• 02: Unknown
• 03-04: HP
• 05-06: PP
• 07-08: Offense
• 09-0A: Defense
• 0B: Fight
• 0C: Speed
• 0D: Wisdom
• 0E: Strength
• 0F: Force
• 10-17: Attacks
• 18-19: Pointer to enemy data
• 1A-1B: Experience
• 1C-1D: Money
• 1E:
  • Bit 1: Having asthma attack
  • Bit 5: Roped
  • Bit 7: Blinded
• 1F: Graphic tileset